Light-sheet microscopy with length-adaptive Bessel beams

Interferometric modulation for generating extended light sheet: improving field of view

Significance

Light-sheet fluorescence microscopy (LSFM) has emerged as a powerful and versatile imaging technique renowned for its remarkable features, including high-speed 3D tomography, minimal photobleaching, and low phototoxicity. The interference light-sheet fluorescence microscope, with its larger field of view (FOV) and more uniform axial resolution, possesses significant potential for a wide range of applications in biology and medicine.

Aim

The aim of this study is to investigate the interference behavior among multiple light sheets (LSs) in LSFM and optimize the FOV and resolution of the light-sheet fluorescence microscope.

Approach

We conducted a detailed investigation of the interference effects among LSs through theoretical derivation and numerical simulations, aiming to find optimal parameters. Subsequently, we constructed a customized system of multi-LSFM that incorporates both interference light sheets (ILS) and noninterference light-sheet configurations. We performed beam imaging and microsphere imaging tests to evaluate the FOV and axial resolution of these systems.

Results

Using our custom-designed light-sheet fluorescence microscope, we captured the intensity distribution profiles of both interference and noninterference light sheets (NILS). Additionally, we conducted imaging tests on microspheres to assess their imaging outcomes. The ILS not only exhibits a larger FOV compared to the NILS but also demonstrates a more uniform axial resolution.

Conclusions

By effectively modulating the interference among multiple LSs, it is possible to optimize the intensity distribution of the LSs, expand the FOV, and achieve a more uniform axial resolution.

Dual-slit confocal light-sheet microscopy using birefringent crystals

We present a method to use a birefringent crystal for generating two illumination beams in a digital scanned laser light-sheet microscopy (DSLM) system. Upon this, a conventional confocal DSLM can be easily upgraded to a dual-slit confocal DSLM with two-fold imaging speed. We have implemented this method to our bidirectional DSLM system, locating two identical calcite crystals on both illumination paths from both sides of the sample. The neurons of in vivo larval zebrafish have been fast imaged with sterling image quality, especially ~2.5 times higher contrast, compared to the conventional DSLM.

Selective plane illumination microscope dedicated to volumetric imaging in microfluidic chambers

In this article, we are presenting an original selective plane illumination fluorescence microscope dedicated to image "Organ-on-chip"-like biostructures in microfluidic chips. In order to be able to morphologically analyze volumetric samples in development at the cellular scale inside microfluidic chambers, the setup presents a compromise between relatively large field of view (∼ 200 µm) and moderate resolution (∼ 5 µm). The microscope is based on a simple design, built around the chip and its microfluidic environment to allow 3D imaging inside the chip. In particular, the sample remains horizontally avoiding to disturb the fluidics phenomena. The experimental setup, its optical characterization and the first volumetric images are reported.

Multicolor light-sheet microscopy for a large field of view imaging: A comparative study between Bessel and Gaussian light-sheets configurations

Light-sheet fluorescence microscopy (LSFM) is useful for developmental biology studies, which require a simultaneous visualization of dynamic microstructures over large fields of views (FOVs). A comparative study between multicolor Bessel and Gaussian-based LSFM systems is presented. Discussing the chromatic implications to achieve colocalized and large FOVs when both optical arrays are implemented under the same excitation objective is the purpose of this work. The light-sheets FOVs, optical sectioning, and resolution are experimentally characterized and discussed. The advantages of using Bessel beams and the main drawbacks of using Gaussian beams for multicolor imaging are highlighted. Multiple Bessel excitation minimizes the FOV's mismatch's effects due to the beams chromatic defocusing and alleviates the aside object blurring obtained with multiple Gaussian beams. It also offers a fair homogeneous axial resolution and optical sectioning over a larger effective FOV. Imaging over perithecia samples of the fungus Sordaria macrospora demonstrates such advantages. This work complements previous comparative studies that discuss only single wavelengths light-sheets excitations.

Characterization of white-light non-diffracting beams generated using a deformable mirror

White-light non-diffraction beams such as Airy beam and Bessel beam have potential applications in multispectral imaging and micromanipulation. Generation of white-light Airy beam and Bessel beam with high quality and high efficiency still remains challenging for conventional diffractive or refractive optics which suffers from significant chromatic dispersion. In this paper, both high-quality white-light Airy beam and Bessel beam are generated using a deformable mirror by modulating the incident LED beam with tunable cubic and conical wavefronts. The main lobe of the generated white-light non-diffraction beams does not suffer from chromatic dispersion along the propagation. The results also show that the generation of the white-light Bessel beam has higher requirements for spatial coherence than white-light Airy beams. Our work expands the understanding of the white-light non-diffraction beams and paves the way for the applications.

Wide field light-sheet microscopy with lens-axicon controlled two-photon Bessel beam illumination

Two-photon excitation can lower phototoxicity and improve penetration depth, but its narrow excitation range restricts its applications in light-sheet microscopy. Here, we propose simple illumination optics, a lens-axicon triplet composed of an axicon and two convex lenses, to generate longer extent Bessel beams. This unit can stretch the beam full width at half maximum of 600-1000 μm with less than a 4-μm waist when using a 10× illumination lens. A two-photon excitation digital scanned light-sheet microscope possessing this range of field of view and ~2-3-μm axial resolution is constructed and used to analyze the cellular dynamics over the whole body of medaka fish. We demonstrate long-term time-lapse observations over several days and high-speed recording with ~3 mm3 volume per 4 s of the embryos. Our system is minimal and suppresses laser power loss, which can broaden applications of two-photon excitation in light-sheet microscopy.

Generating Bessel-Gaussian Beams with Controlled Axial Intensity Distribution

This paper investigated the diffraction of a Gaussian laser beam on a binary mask and a refractive axicon. The principles of the formation of a zero-order Bessel beam with sharp drops of the axial field intensity edges were discussed. A laser optical system based on an axicon for the formation of a Bessel beam with quasi-uniform distribution of axial field intensity was proposed. In the laser optical system, the influence of the axicon apex did not affect the output beam. The results of theoretical and experimental studies are presented. It is expected that the research results will have practical application in optical tweezers, imaging systems, as well as laser technologies using high-power radiation.

Cell and tissue manipulation with ultrashort infrared laser pulses in light-sheet microscopy

Three-dimensional live imaging has become an indispensable technique in the fields of cell, developmental and neural biology. Precise spatio-temporal manipulation of biological entities is often required for a deeper functional understanding of the underlying biological process. Here we present a home-built integrated framework and optical design that combines three-dimensional light-sheet imaging over time with precise spatio-temporal optical manipulations induced by short infrared laser pulses. We demonstrate their potential for sub-cellular ablation of neurons and nuclei, tissue cauterization and optogenetics by using the Drosophila melanogaster and zebrafish model systems.